1. Field of the Invention
This invention relates to a bellows-shaped joint boot made of resin mainly used for a tripod type constant velocity joint, etc. of automobiles.
2. Description of Related Art
As one of constant velocity joints used for driveshafts or the like for vehicles, a tripod type of joint is known in the art.
A tripod type constant velocity joint is, as shown in FIGS. 9, 10 by way of example, comprised of a tripod 4 constructed so that three trunnions 3 having rollers 2 are provided to the one shaft 1 of an input side and an output side shafts in a manner projecting in normal direction to the axis, and an outer housing 6 provided at an end of the other shaft 5. The outer housing 6 has on its inner periphery three axially extending sliding grooves 6a corresponding to the tripod 4. The constant velocity joint is constructed so that the rollers 2 of the tripod 4 are mated with the sliding grooves 6a to be slidably movable in the axial direction, thereby enabling a running torque to be transmitted while enabling the angulation of both shafts 1, 5.
In such constant velocity joint as this, in order to prevent the ingress of dust or foreign substances within the joint or to retain grease contained therein, it is a general practice to mount a joint boot 100 assuming a bellows shape capable of proper extension and contraction and bending deformation so as to cover the part of the shaft 1 on the tripod 4 side from the outer housing 6. The axially one end of the joint boot 100 is formed as a large-diameter attachment part 101 that is attached and fitted to the outer periphery of the outer housing 6 and fixed by a clamping member 7 such as a ring-shaped band or the like, whereas the other end thereof is formed as a small-diameter attachment part 102 that is fixed to and around the outer periphery of the shaft 1 on the tripod 4 side by a clamping member 8, e.g. a ring-like band or the like, and both 101, 102 are connected integrally through a bellows part 103.
As shown in FIG. 10, the outer housing 6 is provided, on its external periphery, with three recessed portions 6b equidistantly disposed in the circumferential direction, corresponding to the arrangement of the sliding grooves 6a on its internal periphery, and accordingly, the external peripheral contour of the outer housing 6 is configured in a non-circular shape constituting a tongued and grooved form in the circumferential direction. Therefore the large-diameter attachment part 101 of the joint boot 100 to be attached to the outer housing 6 assumes, in its external peripheral configuration, a circular form in cross-section and, in its internal peripheral configuration, a non-circular form conforming to the external peripheral configuration of the outer housing 6. That is, on the internal periphery of the large-diameter attachment part 101 there are provided lobe portions 104 protruding inwardly in three circumferential places corresponding to the recessed portions 6b of the outer housing 6 (cf. EP Patent Publication 0915264 A2; JP Patent Application Publication 2003-329057 A).